Springer Online Journal Archives 1860-2000
Summary The present work deals with the mode of trivalent formation and the analysis of trivalent configurations in PMCs of Trillium Hagae (2n=15), an allotriploid species. The important findings are as follows. 1. As for the pairing of chromosomes, the simultaneous pairing of parts of all three homologous chromosomes is possible, though it occurs rather rarely. 2. At the first metaphase, the following three kinds of trivalents are distinguishable: (I) a type with the association of the three kinetochores (IIIK type), (II) a type with the association of any two of the three kinetochores (IIIK' type) and (III) a type in which the three homologues are held together by means of chiasmata only (IIIk type). 3. Several special configurations which are regarded as critical in connection with the origin of chiasmata are described and reasonably interpreted on the basis of a new concept of the two-plane theory.
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